How do you store backup of your files/system etc?

Hey
For a long time I've been storing my backup in external HDD. Every time I wanted to make a backup I simply take it from the drawer, plug in with two way USB (i store this HDD in external case for protection) and start backup. But I thought of idea of doing back up to a micro SD card. I got a HDD with 250 GB and 2 micro SD with 128 GB each. Is it better to use micro SD cards or HDD for back up? Cards are smaller thus easier to store, but at the same time, easier to lose or break. With HDD they are safe to store and relatively cheap, but micro SD cards are cheap too. I can even hide one under my phone case for safety.

How do you store your backup files and which way do you think is better and safer?

Mirrored NAS drive. Google Drive for really important stuff.

I store backup files in a separate folder that's synced with Google Drive.
I typically export one backup for each build version I make, so I mention the build version + describe the main focus of the build in the backup file name. E.g. "Fireside Hero_optimisation_pointer_collider_improvements (0.9.9)"
Once in a while I move part of the backups (which are very unlikely to be ever used) to a local folder. If I'm running into disk space issue, I'm going to delete those.